This invention generally relates to a metal slitting apparatus and, more particularly, to a knife device for slitting sheet metal.
It is known that in sheet metal slitting, devices are used that have upper and lower cutting knives between which the metal is passed to accomplish the desired slitting or edging operation. Typically such devices use circular cutting knives rotatably mounted on shafts, one knife being fixed and the other being adjustable to accommodate varying metal thicknesses or tool placement.
In previous designs, the cutting knife is clamped to one end of the mounting shaft while the opposite end of the mounting shaft is rotatably mounted within a housing. A disadvantage of this design is that the imprecision of the cutting assembly connection causes cutting knife clearance changes in the cutting engagement, such that the knife does not maintain its setting and thus increases knife wear as well as producing inexact cut edges in the metal. Not only is this an undesirable result when the stock being cut requires a uniform and precise cut, but the operation is also more expensive because the service life of the cutting knives is shortened.
An attempt has been made to alleviate premature knife wear and the resulting imprecise slitting or edging by placing the cutting knife at an angle opposite the direction of the feed of the sheet metal, with the idea that the rotation plane of the inclined cutting knife will diverge from the direction of the cut edge of the sheet metal by the amount that the cutting knife is angled. This has been accomplished by placing the mounting shaft of one of the cutting knives at an angle with the sheet metal. This technique has provided some favorable results; however, the problems previously mentioned still exist.
In addition, premature knife wear and inexact cut edges result from the play occurring in the connection between the mounting shaft and the housing, specifically with the location of the shaft bearings within the housing. This play existing between the mounting shaft and the bearings causes the cutting knife to slightly wobble, causing the cutting knife to make contact with the lower knife, thereby causing excessive wear on the knife as well as producing an inexact cut. Therefore, a need exists for an improved knife holder design that eliminates the problems associated with previous cutting knife assemblies, and produces exact cuts as well as extending the service life for the cutting tool.